Engine Cooling problem
2004 GMC Envoy 6 cyl Four Wheel Drive Automatic 116k miles
I am having an overheating problem with my truck that started about a month ago, the gauge sometimes reads about 250F with the AC on but when the AC is off it is around 215 -220. I replaced the thermostat, waterpump, coolant temp sensor and the fan clutch and flushed the coolant several times but it is still overheating. There is no coolant loss or coolant oil mix or smoke and there is no performance loss, and it doesn't throw any error codes, could it be a clogged radiator or a blown head gasket, what is the next thing to check, will the dirty transmission oil, that has never been changed, cause engine overheating. The ambient temperature here in Arizona is around 112F.
My 04 Envoy is doing the same thing. I am in New Mexico and replace everthing as well. 2 weeks in the shop and still it overheats when the ac is on. Could a valve/ head be causing a problem. I read that some removed the head, cleaned and ground the valves and now seems to be ok. Yes I am a women, who does not have a clue about auto repairs, This is getting costly!